Back to EveryPatent.com
United States Patent |
6,166,117
|
Miyazaki
|
December 26, 2000
|
Water-soluble film
Abstract
A water-soluble film, comprising 100 parts by weight of (A) a sulfonic acid
group modified polyvinyl alcohol and 0.05-20 parts by weight of (B) gallic
acid, salts thereof or a C.sub.1-5 alkyl ester thereof.
Inventors:
|
Miyazaki; Hirotoshi (Kurashiki, JP)
|
Assignee:
|
Kuraray Co., Ltd. (Kurashiki, JP)
|
Appl. No.:
|
094506 |
Filed:
|
June 10, 1998 |
Foreign Application Priority Data
| Jun 11, 1997[JP] | 9-153227 |
| Dec 03, 1997[JP] | 9-332706 |
Current U.S. Class: |
524/291; 524/284; 525/58; 525/59; 525/61 |
Intern'l Class: |
C08K 005/09 |
Field of Search: |
524/291,284
525/58,59,61
|
References Cited
U.S. Patent Documents
4156047 | May., 1979 | Wysong.
| |
4221710 | Sep., 1980 | Hoshi et al. | 252/316.
|
4753947 | Jun., 1988 | Dorn et al. | 514/277.
|
4833116 | May., 1989 | Yamori et al. | 503/200.
|
4910185 | Mar., 1990 | Satake et al. | 503/210.
|
4954477 | Sep., 1990 | Shuku et al. | 503/226.
|
5677365 | Oct., 1997 | Kikuta et al. | 523/201.
|
Foreign Patent Documents |
0 259 037 | Mar., 1988 | EP.
| |
53-24351 | Mar., 1978 | JP.
| |
7-118407 | May., 1995 | JP.
| |
9-316270 | Dec., 1997 | JP.
| |
Other References
Patent Abstracts of Japan, vol. 095, No. 008, Sep. 29, 1995, JP 07 118 407,
May 9, 1995.
|
Primary Examiner: Reddick; Judy M.
Attorney, Agent or Firm: Oblon, Spivak, McClelland, Maier & Neustadt, P.C.
Claims
What is claimed as new and is intended to be secured by Letters Patent is:
1. A water-soluble film, comprising:
100 parts by weight of (A) a sulfonic acid group modified polyvinyl alcohol
and 0.50-20 parts by weight of (B) gallic acid, its salts or a C.sub.1-5
alkyl ester thereof.
2. The water-soluble film of claim 1, wherein said gallic acid ester is the
methyl, ethyl, propyl or isoamyl ester.
3. The water-soluble film of claim 1, wherein the amount of gallic acid or
a C.sub.1-5 -alkyl ester thereof ranges form 0.2-10 parts by weight.
4. The water-soluble film of claim 1, wherein the content of the sulfonic
acid group unit in the polyvinyl alcohol ranges form 0.1-20 mol. %.
5. The water-soluble film of claim 4, wherein the content of the sulfonic
acid group unit ranges from 0.5-10 mol. %.
6. The water-soluble film of claim 1, wherein the polyvinyl alcohol is
prepared from a sulfonic acid group containing monomer selected from the
group consisting of 2-acrylamido-2-methylpropanesulfonic acid,
2-methacrylamido-2-methylpropanesulfonic acid, salts thereof and olefin
sulfonic acids.
7. The water-soluble film of claim 1, wherein the degree of hydrolysis of
the polyvinyl alcohol ranges form 50-100 mol. %.
8. The water-soluble film of claim 7, wherein said degree of hydrolysis
ranges from 80-100 mol. %.
9. The water-soluble film of claim 1, wherein the sulfonic acid group
modified polyvinyl alcohol is prepared by the copolymerization of a vinyl
ester a sulfonic acid group containing a monomer.
10. The water-soluble film of claim 9, wherein the polyvinyl alcohol is
prepared by the reaction of a sulfonic acid containing compound with
polyvinyl alcohol.
11. The water-soluble film of claim 1, wherein the polyvinyl alcohol is
prepared by the reaction of a sulfonic acid containing compound with
polyvinyl alcohol.
12. A composition, comprising:
100 parts by weight of (A) a sulfonic acid group modified polyvinyl alcohol
and 0.05-20 parts by weight of (B) gallic acid, salts thereof or a
C.sub.1-5 alkyl ester thereof.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a polyvinyl alcohol (hereinafter referred
to as PVA) film having excellent properties which make it suitable for use
in the packaging of chemicals such as agricultural chemicals,
microbiocides, and the like.
2. Description of the Background
A method of unit-dose packaging (unit pack) various chemicals such as
agricultural chemicals under airtight packaging conditions in a
water-soluble film has been recently employed, where the chemicals in
packaged form are thrown into water so that the contents are dissolved or
dispersed in water. The unit pack is advantageous in that users do not
directly touch harmful chemicals, the measurement of chemicals for use in
unnecessary as the unit-dose is already packaged, and the disposal of the
containers and bags used for packaging chemicals is unnecessary or is
easy.
Partially-hydrolyzed PVA films have been used in the past as water-soluble
films for a unit pack. The conventional water-soluble films exhibit
excellent cold water-solubility and mechanical strength. However, some
types of chemicals, which are packaged in these films, cause problems by
lowering the water-solubility of the films with the passage fo time during
storage to the point that the films finally become water-insoluble or
hardly soluble in water.
Chemicals which cause partially-hydrolyzed PVA films to become
water-insoluble include, for example, alkali chemical substances, acid
chemical substances, chlorine-containing chemical substances, chemical
compounds of a salt of a polyvalent metal such as copper, cobalt, or the
like, polycarboxylic acid containing chemical substances,
polyamine-containing chemical substances, boric acid-containing chemical
substances, agricultural chemicals such as insecticides, herbicides, and
the like, and microbiocides.
Films for packaging alkali chemical substances which are known include
films of PVA modified with salts of carboxylic acids. A film which is
resistant to boric acid is a sorbitol-containing PVA film.
Known films for packaging acid chemical substances, chlorine-containing
chemical substances (microbiocides, etc.) and agricultural chemicals
include films fo polyethylene oxide and cellulose, However these films are
defective in that their water-solubility is extremely low, their
mechanical properties are poor, and their impact resistance at low
temperatures is extremely low because they are hard and brittle.
Films which are known for packaging agricultural chemicals and
microbiocides include water-soluble films that are prepared from PVA or
carboxylate-modified PVA, wherein the polymer is combined with an
auxiliary such as polyethylene glycol or propyl gallate. (See Japanese
Patent Application Laid-Open No. Sho-53-24351 (1978).) Also water-soluble
films for packaging agricultural chemicals are known, which are prepared
from sodium 2-acrylamido-2-methylpropanesulfonate-modified PVA having
added thereto a phenol derivative such as bisphenol A. (See JP
Hei-7-118407 (1995).) However, in the event chemicals such as acid
chemical substances, chlorine-containing chemical substances, agricultural
chemicals and microbiocides are packaged in the conventional PVA films and
stored for a long period, the PVA films lose their function as a
water-soluble film, because they become discolored (a brown color) and
become insoluble in cold water and hot water. A need continues to exist
for a PVA based packaging film which is resistant to various chemical
materials which are stored therein.
SUMMARY OF THE INVENTION
Accordingly, one object of the present invention is to provide a
water-soluble film which has excellent mechanical strength, which has
softness and toughness, and moreover which can maintain its original
water-solubility when such chemicals as agricultural chemicals and
microbiocides are packaged therein and stored for long periods of time.
Another object of the present invention is to provide a package for acidic
chemical substances, chlorine-containing chemical substances and
agricultural chemicals which is formed of a water-soluble film.
Still another object of the present invention is to provide a composition
which can favorably be used as a material for the production of
water-soluble films.
Briefly, these objects and other objects of the present invention as
hereinafter will become more readily apparent can be attained by a
water-soluble film comprising 100 parts by weight of (A) a sulfonic acid
group modified polyvinyl alcohol and 0.05-20 parts by weight of (B) gallic
acid, salts thereof or a C.sub.1-5 alkyl ester thereof.
Another aspect of the invention is directed to a composition for the film
which is as defined above.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
The sulfonic acid group modified PVA (A) of the present invention is, for
example, a hydrolyzate of a copolymer prepared from a vinyl ester and a
sulfonic acid group containing monomer, or can be a polymer which is
prepared by the addition of a sulfonic acid group-containing compound to
PVA hydrolyzak of polyvinyl ester).
The hydrolyzate of a copolymer of a vinyl ester and a sulfonic acid
group-containing monomer is obtained by copolymerizing, in the presence of
a radical initiator, a vinyl ester and a sulfonic acid group-containing
monomer in bulk or in a solvent such as an alcohol, followed by partially
or extensively hydrolyzing the copolymer with an alkali or acid catalyst.
Suitable vinyl esters include, for example, vinyl acetate, vinyl
propionate, vinyl formate, vinyl versate, vinyl pivalate, and the like. Of
these monomers, vinyl acetate is preferred, because it is produced on an
industrial scale and is favorable from the aspect of cost.
Any sulfonic acid group-containing monomer can be used insofar as it has a
sulfonic acid group or a salt thereof in the molecule and is
copolymerizable with a vinyl ester. Suitable examples include
2-acrylamido-2-methylpropanesulfonic acid,
2-acrylamido-1-methylpropanesulfonic acid,
2-methacrylamido-2-methylpropanesulfonic acid, and alkali metal salts
thereof; olefin sulfonic acids such as ethylensulfonic acid,
allylsulfonic, acid, methallylsulfonic acid, and alkali metal salts
thereof. Of these, most preferred are 2-acrylamido-2-methylpropanesulfonic
acid and alkali metal salts thereof, because of their copolymerizability
with vinyl esters and their stability during hydrolysis. Suitable alkali
metals include Na, K, Li, and the like. Also within the scope of the
invention are sulfonic acid salts of ammonia, amines, and the like. The
sulfonic acid group in acid form is an embodiment of the invention.
However, preferably the group is partially or completely neutralized with
an alkali metal in order to prevent the vinyl ester from being hydrolyzed
during copolymerization.
The copolymer of the vinyl ester and the sulfonic acid group-containing
monomer is then hydrolyzed with an alkali or acid catalyst in an alcohol
solution to give the modified PVA containing sulfonic acid groups.
The polymer which is prepared by the addition of a sulfonic acid
group-containing compound to PVA hydrolyzate of polyvinyl ester) is a
polymer which is prepared by introduction of a sulfonic acid
group-containing compound into PVA by acetalization or by a Michael
addition reaction.
For the introduction of the sulfonic acid group containing compound into
the polymer by acetalization, the aldehyde compound employed has a
sulfonic acid group such as a salt of butylaldehydosulfonic acid or a salt
of benzaldehydosulfonic acid.
The sulfonic acid group-containing compound which is employed as a reactant
in the Michael addition reaction is an unsaturated sulfonic acid
group-containing compound such as 2-acrylamido-2-methylpropanesulfonic
acid, allylsulfonic acid, or alkali metal salts thereof.
Other than the above methods, a suitable method is the addition of a
sulfonic acid group-containing alcohol compound to PVA by electrification.
Still another reaction is the introduction of a sulfonic acid
group-containing halide compound into PVA by a condensation reaction.
The content of sulfonic acid group unit in the modified PVA (A) preferably
ranges from 0.1-20 mol. %. more preferably from 0.5-10mol. %, most
preferably from 1-5 mol. %.
The mechanical properties of the water-soluble film are also important, and
strength and flexibility of the film are necessary even in the case of a
thin thickness of 10-100 .mu.m. Therefore, the viscosity-average degree fo
polymerization (hereinafter referred to a degree of polymerization) of the
modified PVA (A) is preferably 300-10000, more preferably 500-8000. In the
case where the degree fo polymerization is less than 300, the film
strength is less. In the case where the degree fo polymerization is more
than 10000, the viscosity of the solution during preparation of the film
is so high that the workability is lessened.
Since the film has to be water-soluble and resistant to chemicals, the
degree of hydrolysis of the modified PVA (A) is 50-100 mol. %, preferably
80-100 mol. %. Such a degree of hydrolysis is also required in view of the
strength and toughness requirements of the film and the workability of the
into bags.
The gallic acid or C.sub.1-5 alkyl ester thereof (B), which is a component
of the present invention film, is a compound whose function is to prevent
the water-soluble film from becoming water-insoluble. Suitable examples
include gallic acid, its salts, and its esters such as methyl, ethyl,
propyl, isoamyl, and the like. If these compounds, the most preferred are
gallic acid and propyl gallate (propyl ester of gallic acid).
The amount of component (B) in the film ranges from 0.05-20 parts by
weight, preferably 0.2-10 parts by weight, more preferably 0.5-3 parts by
weight, based on 100 parts by weight of component (A). In the event where
the amount of component (B) is less than 0.05 parts by weight, the
water-solubility of the film is decreased and the film becomes
water-insoluble when chemicals are packaged in the film and stored. On the
other hand, in the case where the amount of component (B) is more than 20
parts by weight, the film strength is substantially decreased and, in
addition, white powder migrates onto the surface of the film.
In addition to components (A) and (B) of the film, loading of the
water-soluble film of the present invention with a reducing
hydroxycarboxylic acid (C) can improve the films stability during storage
and furthermore prevent discoloration because of the presence of a
polyvalent metal ion such as iron ion.
Suitable reducing hydroxycarboxylic acids. (C) include, for example, citric
acid, tartaric acid, L-ascorbic acid, malic acid, racemic acid, and salts
thereof. Of these, citric acid, tartaric acid and L-ascorbic acid are
preferred. Particularly preferred is citric acid. The amount of the
component (C) preferably ranges from 0.01-10 parts by weight, more
preferably form 0.05-5 parts by weight, most preferably 0.1-3 parts by
weight, based on 100 parts by weight of PVA (A).
Since the water-soluble film of the present invention is transported,
stored and used even in high-temperature and high-humidity districts and
cold-temperature districts, the strength and toughness of the film are
important and essential characteristics. In particular, it is necessary
for the film to have good impact resistance at low temperature, and
therefore various plasticizers can be added for the purpose of lowering
the glass transition temperature of the film. Suitable examples include
polyalcohols such as glycerin, diglycerin, diethylene glycol, and the
like; polyethers such as polyethylene glycol, polypropylene glycol, and
the like; phenol derivatives such as bisphenol A, bisphenol S, and the
like; amide compounds such as N-methylpyrrolidone, and the like; phenol
derivatives such as as glycerin, pentaerythritol, sorbitol, and the like
with ethylene oxide; water, and the like. These plasticizers can be used
alone or in combination.
Method of producing the film include, for example, a method in which
component (B) and optionally component (C) are added to an aqueous
solution of the modified PVA (A), followed by dissolving or dispersing
these materials, and thereafter casting the solution or dispersion onto a
film. Another method is to melt-extrude the materials in the presence of a
suitable plasticizer or water into a film. If desired, one or more
ordinary additives such as colorants, fragrances, vehicles, defoaming
agents, mod-release agents, ultraviolet absorbents, inorganic powders,
surfactants, preservatives, antifungal agents and the like, may be added.
Further if desired, a water-soluble polymer such as PVA other than
component (A), starch, carboxymethyl cellulose, methyl cellulose,
hydroxymethyl cellulose and the like, may also be added thereto within a
range which does not impair the characteristics of the film of the present
invention.
As the chemicals which are packaged in the water-soluble film of the
present invention, preferred are acid chemical substances,
chlorine-containing chemical substances, agricultural chemicals,
microbiocides, and the like. Other chemicals such as detergents, dyes,
chemical substances for plantation and cultivation, and the like can be
packaged.
The acid chemical substances are those which are acidic when dissolved or
dispersed in water. Suitable example include agricultural chemicals,
microbiocides, deodorizers, and the like.
Chlorine-containing chemical substances are those which contain chlorine in
the molecule, Suitable examples include agricultural chemicals,
microbiocides, bleaches, and the like. Specific examples include
isocyanuric acid trichloride, isocyanuric acid dichloride, the sodium salt
of isocyanuric acid dichloride, N,N-dichlorohydantoin,
N-chloro-N-bromo-5,5-dimethylhydantoin, and the like.
Agricultural chemicals include chloropicrin, 1,3-dichloropropene,
dichloroisopropyl ether, and the like.
The chemicals may be in any form such as granular, tabletted, powdered or
even liquid. They may be combined with a carrier such as talc, kaolin,
bentonite, diatomaceous earth, or the like; and extender; a surfactant and
a dispersant to improve the affinity of the chemicals for water and to
uniformly disperse the chemicals in water.
The water-soluble film of the present invention provides excellent
advantages because its water-solubility does not diminish with the passage
of time, even when the film is used for the packaging of acidic chemical
substances, chlorine-containing chemical substances or agricultural
chemicals.
The present invention also provides a composition comprising 100 parts by
weight of component (A) and 0.05-20 parts by weight of component (B). It
further provides a composition comprising 100 parts by weight of component
(A) 0.05-20 parts by weight of component (B), and 0.01-10 parts by weight
of component (C). These compositions are advantageously used, not only as
a material for producing the above-mentioned water-soluble film, but also
as a material for producing fiber which is used in non-woven fabrics, and
the like.
Having now generally described the invention, a further understanding can
be obtained by reference to certain specific examples which are provided
herein for purpose of illustration only and are not intended to be
limiting unless otherwise specified. Unless otherwise specifically
indicated, "%" and "part(s)" in the Examples are on weight-basis.
EXAMPLE 1
A methanol solution of sodium hydroxide was added to a methanol solution of
a copolymer which had been prepared by copolymerizing, in methanol, vinyl
acetate and sodium acrylamido-2-methylpropanesulfonate, thereby
hydrolyzing the copolymer to give a modified PVA having a sulfonic acid
group. The modified PVA thus obtained had a degree of polymerization of
1700, a degree of hydrolysis of 88 mol. %, and a sulfonic acid group
content of 2 mol. %.
To 100 parts of the modified PVA, were added 1 part of propyl gallate, 0.2
parts of citric acid, and 20 parts of glycerin as a plasticizer to prepare
a uniform aqueous solution. The solution was cast onto a hot roll at
70.degree. C. to prepare a modified PVA film having a thickness of 40
.mu.m.
This modified PVA film was formed into bags (10.times.15 cm). A 35 g amount
of tablets of a microbiocides for swimming pools, which contained
trichloroisocyanuric acid as the main component, was placed into each bag,
and hot-sealed. Packages were thus obtained (single-wrapped packages)
having the chemicals therein. The outsides of the prepared packages were
furthermore wrapped with a film which was obtained by laminating the
surface of aluminium with polyethylene (hereinafter referred to as
aluminium-laminated film), and hot-sealed to give double-wrapped packages.
The double-wrapped packages having the chemical therein were subjected to
an accelerating test (shelf test) for long-term storage stability, in
which the packages were left in a thermostatic chamber at 40.degree. C.
for 3 months. After storage, the packages were evaluated for changes in
the water-solubility of the PVA film, the degree of discoloration of the
PVA film, and the odor from single-wrapped packages after the
aluminium-laminated film had been removed from the double-wrapped
packages. The methods of each test are shown below. The evaluation results
are shown in Table 1.
Method of Measuring Water-solubility of PVA Film
The PVA film was cut into squares (40 mm.times.40 mm). Each piece was
framed, and dipped in water which was stirred at 20.degree. C. or
10.degree. C. the time (in seconds) was measured until the PVA film
completely dissolved, In the event the PVA film did not dissolve within 30
minutes, it was evaluated as being water-insoluble.
Discoloration of PVA Film
The results obtained were rated in terms of the following symbols
.largecircle.: Not discolored, which means colorless.
.DELTA.: Slightly yellowed.
X: Browned.
Smell from Single-Wrapped Package
The odors of the films were sensually evaluated from single-wrapped
packages after the aluminum-laminated film had been removed from each
double-wrapped package. The results obtained were rated in terms of the
following symbols:
.largecircle.: No odor.
.DELTA.: A little odor.
X: Very strong odor.
EXAMPLE 2
In the same manner as described in Example 1, vinyl acetate and sodium
acrylamido-2-methylpropanesulfonate were copolymerized and hydrolyzed to
prepare a modified PVA having sulfonic acid groups. The modified PVA had a
degree of polymerization of 1250, a degree of hydrolysis of 97 mol. %, and
a sulfonic acid group content of 4 mol. %.
A modified PVA film having a thickness of 40 .mu.m was formed in the same
manner as described in Example, 1, except that 1 part of propyl gallate,
and 0.5 parts of citric acid, and 10 parts of glycerin and 15 parts of
diglycerin, as plasticizers, were added to 100 parts of the modified PVA.
In the same manner as described in Example 1, except that 35 g of tablets
of a microbiocidal detergent for toilets (sodium dichloroisocyanurate
containing a surfactant) was packaged with the modified PVA film prepared
herein , double-wrapped packages were prepared and evaluated. The results
are shown in Table 1.
EXAMPLE 3
In the same manner as described in Example, 1, vinyl acetate and sodium
acrylamido-2-methylpropanesulfonate were copolymerized and hydrolyzed to
prepare a modified PVA containing sulfonic acid groups. The modified PVA
had a degree of polymerization of 1250, a degree of hyudrolysis of 98 mol.
%, and a sulfonic acid group content of 4 mol. %.
A modified PVA film having a thickness of 40 .mu.m was prepared in the same
manner as described in Example 1, except that 0.8 parts of ethyl gallate,
0.3 parts of L-ascorbic acid, and 15 parts of glycerin and 10 parts of
polyethylene glycol #300 as plasticizers were added to 100 parts of the
modified PVA.
In the same manner as described in Example 1, except that a microbiocides
containing bromo, chloro-5,5-dimethylhydantoin was packaged in the
modified PVA film prepared herein, double-wrapped packages were prepared
and evaluated. The results are shown in Table 1.
EXAMPLE 4
A modified PVA film having a thickness of 40 .mu.m was prepared in the same
manner as described in Example 3, except that L-ascorbic acid was not
added.
In the same manner as described in Example 3, except that a microbiocide
containing bromo, chloro-5,5-dimethylhydantoin was packaged in the
modified PVA film prepared herein, double-wrapped packages were prepared
and evaluated. The results are shown in Table 1.
EXAMPLE 5
To an aqueous solution of PVA having a degree of polymerization of 1700 and
a degree of hydrolysis of 99.6 mol. % (This solution was made acidic with
hydrochloric acid.), was added 5 mol. % (based on the amount of vinyl
alcohol units in the PVA) of sulfonic acid benzaldehyde, whereby sulfonic
acid benzaldehyde was added to the PVA by an acetalization reaction. A
modified PVA containing sulfonic acid groups was obtained.
A modified PVA film having a thickness of 40 .mu.m was formed in the same
manner as described in Example 1, except that 2.5 parts of gallic acid, 1
part of tartaric acid, and 10 parts of glycerin and 15 parts of
diglycerin, as plasticizers, were added to 100 parts of the modified PVA.
In the same manner as describe in Example 1, except that a microbiocide for
swimming pools was packaged in the modified PVA film prepared herein,
double-wrapped packages were prepared and evaluated. The results are shown
in Table 1.
COMPARATIVE EXAMPLE 1
A modified PVA film having a thickness of 40 .mu.m was prepared in the same
manner as described in Example 1, except that propyl gallate and citric
acid were not added.
In the same manner as described in Example 1, except that a microbiocide
for swimming pools was packaged in the modified PVA film prepared herein,
double-wrapped packages were prepared and evaluated. The results are shown
in Table 1.
COMPARATIVE EXAMPLE 2
A modified PVA film having a thickness of 40 .mu.m was prepared in the same
manner as described in Example 2, except that propyl gallate was not
added.
In the same manner as described in Example 2, except that a microbiocidal
detergent for toilets was packaged in the modified PVA film prepared
herein, double-wrapped packages were prepared and evaluated. The results
are shown in Table 1.
COMPARATIVE EXAMPLE 3
A non-modified PVA film having a thickness of 40 .mu.m was prepared in the
same manner as described in Example 1, except that a non-modified PVA
having a degree fo polymerization of 700 and a degree of hydrolysis of 88
mol. % was used instead of the modified PVA containing sulfonic acid
groups.
In the same manner as described in Example 1, except that a mocrobiocide
for swimming pools was packaged in the non-modified PVA film prepared
herein, double-wrapped packages were prepared and evaluated. The results
are shown in Table 1.
COMPARATIVE EXAMPLE 4
A modified PVA film having a thickness of 40 .mu.m was prepared in the same
manner as described in Example 1, except that 7 parts of bisphenol A was
added instead of propyl gallate.
In the same manner as described in Example 1, except that a mocrobiocide
for swimming pools was packaged in the modified PVA film prepared herein,
double-wrapped packages were prepared and evaluated. The results are shown
in Table 1.
TABLE 1
__________________________________________________________________________
After Shelf Test at 40.degree. C. for 3 Months
Before Shelf Test Odor from
Water-solubility of PVA Water-solubility of PVA Single-
Film.sup.1) Film.sup.1) Discoloration Wrapped
20.degree. C.
10.degree. C.
20.degree. C.
10.degree. C.
of PVA Film.sup.2)
Packages.sup.3)
__________________________________________________________________________
Example 1
19 28 35 58 .largecircle.
.largecircle.
Example 2 14 23 20 27 .largecircle. .largecircle.
Example 3 15 25 28 36 .largecircle. .largecircle.
Example 4 22 35 130 158 .DELTA. .largecircle.
Example 5 21 35 34 46 .largecircle. .largecircle.
Comparative 22 33 water- water- X X
Example 1 insoluble insoluble
Comparative 18 36 water- water- X .DELTA.
Example 2 insoluble insoluble
Comparative 30 68 water- water- X X
Example 3 insoluble insoluble
Comparative 20 31 water- water- X X
Example 4 insoluble insoluble
__________________________________________________________________________
The notes for Table 1 are defined as follows.
.sup.1) Watersolubility of PVA Film: Time (seconds) was measured until th
PVA film completely dissolved.
.sup.2) Discoloration of PVA Film:
.largecircle.: Not discolored, which means colorless.
.DELTA.: Slightly yellowed.
X: Browned.
.sup.3) Odor from singlePackage:
.largecircle.: No odor
.DELTA.: A little odor
X: Very strong odor
The disclosures of Japanese priority applications serial numbers 153227/97
and 332706/97 filed Jun. 11, 1997 and Dec. 3, 1997 are hereby incorporated
by reference.
Obviously, numerous modifications and variations of the present invention
are possible in light of the above teachings. It is therefore to be
understood that within the scope of the appended claims, the invention may
be practiced otherwise than as specifically described herein.
Top